Normally, welding tongs with a pneumatic drive device for generating a respective electrode power are used nowadays in industry, for instance in the automobile production. The pneumatic drive devices causes, particularly if the welding tongs are formed with a pair of limbs or double-armed levers, these limbs or levers to be moved from their standby position into their welding position, in which they oppositely press onto sheets to be welded together. Upon reaching an adequate electrode power, a welding current is supplied to the welding tongs and the welding of the sheets takes place. Subsequently, the limbs of the welding tongs, hereinafter referred to as levers, are moved back into their standby position and the welding tongs are moved for instance by means of a robot to the next welding position.
When using welding tongs with a pneumatic drive device it turned out that the drive is relatively uncomplicated and easy to maintain and can be controlled and monitored in a simple way. However, the electrode power in a pneumatic drive device can hardly be controlled during the welding process. When adjusting the levers to the standby position, the welding electrodes impinge onto the workpiece. Neither during adjustment of the levers from the standby position to the welding position nor vice versa during the welding process is a position monitoring of the levels by means of the drive device possible. The pneumatic operation of the drive device also leads to a high noise level and great effort for the installation of the respective pneumatic supply system. Moreover, air permanently escapes, which leads to a further noise pollution.
Moreover, it must be noted that the pneumatic drive device's construction length between the adjustment lever ends is relatively large. The construction length is, however, important in connection with the maximum possible opening angle of the levers. That means that if the construction length of the drive device and the lever length is predefined, the maximum opening angle of the level in the standby position results, which is variable only by changing the construction length or the lever length. The size of the maximum opening angle is important to be able to move the welding tongs from one welding position to the other without colliding with the workpiece.